1. Field of the Invention
The present invention relates to a digital camera and an image-capturing control apparatus that employ an image-capturing device such as a CCD to capture an image of a subject.
2. Description of the Related Art
Digital cameras in the known art include those provided with an image-capturing device such as a CCD that outputs image data by capturing a subject image passing through a taking lens and an image signal processing circuit that removes noise from image signals output by the image-capturing device by utilizing a correlated double sampling (CDS) circuit or the like.
In such a digital camera in the prior art, the operating timing of the sampling circuit that performs sampling in conformance to the timing with which image signals are output by the image-capturing device, the operating timing of the clamp circuit that samples image signals during black level periods in conformance to the above timing in order to set the black level of the image signals at a specific value and the operating timing of the A/D conversion circuit that converts the analog image signals having been sampled by the circuits mentioned above to digital image signals are adjusted so as to match with one another.
When a component used in any of the circuits is changed, it may be necessary to modify the operating timing in correspondence to the new particulars of the component. In addition, any changes in the temperature during an operation of an electronic component used in any of the circuits or changes in the voltage applied to the electronic component usually cause changes in its operating timing. Thus, if the digital camera is operated under operating conditions in which the temperature changes greatly or if the voltage at a circuit becomes lowered due to depletion of the battery in the digital camera, the operating timing of the circuit may change. This poses a serious problem particularly when the digital camera is a high image quality digital camera with a large number of pixels provided at the image-capturing device, in which image signals resulting from an image-capturing operation are sampled at high speed or when the digital camera is used continuously over a long period of time.